Point‐Source Extraction with MOPEX

MOPEX (Mosaicking and Point‐source Extraction) is a package developed at the Spitzer Science Center for astronomical image processing. We report on the point‐source extraction capabilities of MOPEX. Point‐source extraction is implemented as a two‐step process: point‐source detection and profile fitting. Nonlinear matched filtering of input images can be performed optionally to increase the signal‐to‐noise ratio and improve detection of faint point sources. Point response function (PRF) fitting of point sources produces the final point‐source list, which includes the fluxes and improved positions of the point sources, along with other parameters characterizing the fit. Passive and active deblending allows for successful fitting of confused point sources. Aperture photometry can also be computed for every extracted point source for an unlimited number of aperture sizes. The PRF is estimated directly from the input images. The implementation of efficient methods of background and noise estimation and a modified simplex algorithm contribute to the computational efficiency of MOPEX. The package is implemented as a loosely connected set of Perl scripts, each script running a number of modules written in C/C++. Input parameter setting is done through name lists, ASCII configuration files. We present applications of point‐source extraction to the mosaic images taken at 24 and 70 μm with the Multiband Imaging Photometer (MIPS) as part of the Spitzer extragalactic First Look Survey, and to a Digital Sky Survey image. Completeness and reliability of point‐source extraction is computed using simulated data.